Astronomers are getting closer than ever to seeing the supermassive black hole at the center of the galaxy M87, which is shown here in a combination of radio (red) and X-ray (blue) wavelengths. The image shows "jets" of charged particles shooting away from the black hole, which is about 6.6 billion times as massive as the Sun and three times wider than Pluto's orbit around the Sun. Although the black hole is 50 million light-years away, it is so huge that it presents the best chance for astronomers to actually photograph a black hole's event horizon -- the point of no escape for anything that falls into the black hole. Such an image could be snapped sometime in the next couple of years, according to Texas astronomer Karl Gebhardt, who made the most accurate measurement of the black hole's mass to date. [NASA/CXC/KIPAC/N. Werner, E. Million et al/NRAO/AUI/NSF/F. Owen]
No one has ever seen a black hole. That makes sense, because black holes are completely black -- nothing escapes from them, including light. Yet astronomers have discovered hundreds of them -- including some monsters that are bigger than our solar system. They use a variety of techniques to find the black holes -- they just don't actually see them.
The biggest and most massive black hole for which astronomers have a good measurement is at the heart of the galaxy M87.
GEBHARDT: The black hole mass we measure is 6.6 billion times the mass of the Sun -- it's the biggest black hole in the nearby universe.
That's Texas astronomer Karl Gebhardt, who led a team that measured the black hole's mass. The team measured the motions of stars not far from the black hole, which are accelerated by the black hole's powerful gravity.
M87's black hole is so large that one day astronomers should be able to take a picture of its event horizon -- what makes the black hole black; anything that crosses the event horizon is gone for good. That would offer the final proof that black holes really exist.
GEBHARDT: It's about three times the size of Pluto's orbit -- just the event horizon alone. And it could swallow our solar system whole if it happened to wander too near to us -- that's not going to happen. But it is the best candidate we have for trying to observe the event horizon. We don't know whether black holes are black holes. To actually determine if an object is a black hole, you need to have some type of proof of an event horizon -- that's the defining property of the black hole. And that doesn't exist yet.
Script by Damond Benningfield, Copyright 2011
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